7 Common Uncool Yet Avoidable PCB Failures

How many of you have had an atrocious experience when dealing with suppliers for your PCB/PCBA? And when I say atrocious, it means a hell of a load of bad experiences that you've literally been through due to receiving bad quality boards and poor services from the supplier. Let's take a look at the following 7 common issues we usually face when dealing with your printed circuit board. I hope it doesn't get on your nerves as you're reading this.

1. Bad Soldering

What's the greatest turn off for engineers first thing when they look at the board? I think all would agree it's none other than the badly soldered joints, that's totally uncool for people like me who may have a severe OCD issue.

Common soldering problems include:

• Disturbed joint

For a board that has been subjected to movement as the solder was solidifying, the surface of the joint may appear to be frosted, crystalline or rough. It is what people often called a "cold joint", which looks similarly like a true cold joint, however, the cause is different.

• Cold joint (I mentioned it above)

This is one where the solder did not melt completely. It is often characterized by a rough or lumpy surface. Cold joints are unreliable. The solder bond will be poor and cracks may develop in the joint over time.

• Overheated joint

At the other extreme, we have the overheated joint. The solder has not yet flowed well and the residue of burnt flux will make fixing this joint difficult.

• Insufficient wetting (Pad)

These two joints both show signs of insufficient wetting of the solder pad. The solder has wet the leads nicely, but it has not formed a good bond with the pad. This can be caused by a dirty circuit board or by failing to apply heat to the pad as well as the pin.

• Insufficient wetting (Pin)

This solder in this joint has not wet the pin at all and has only partially wet the pad. In this case, heat was not applied to the pin and the solder was not given adequate time to flow.

• Insufficient wetting (Surface Mount)

Here we have three pins of a surface mount component where the solder has not flowed onto the solder pad. This is caused by heating the pin instead of the pad.

• Solder starved

The joint simply does not have enough solder. It may make good electrical contact, but it is hard to verify by inspection. In any case, it is not a strong joint, and may develop stress cracks and fail over time.

• Too much solder

This might be a perfectly good joint, but we can't tell for sure. It is entirely possible that this blob of solder wets neither the pin nor the pad and is not a reliable electrical connection. The best evidence of proper wetting (and good electrical contact) is a nice concave surface as on the joint on the far left.

• Untrimmed leads

Leads that are too long are potential short circuits. The two joints on the left are in obvious danger of touching. But the one on the right is long enough to be dangerous as well. It would not take much force to bend that lead over to touch an adjacent trace.

• Solder bridge

The left two solder joints have melted together, forming an unintended connection between the two.

• Lifted pad

This photo shows a solder pad that has become detached from the surface of the circuit board. This most often occurs when trying to de-solder components from the board. But it can result simply from overworking the joint to the point where the adhesive bond between copper and the board is destroyed.

So how can we fix all the issues above?

Fret not. Take your time. Most joints can be repaired with patience. If the solder refuses to flow the way you want it to:

• Stop and let the joint cool.

• Clean and tin your iron.

• Clean off any burnt flux from the joint.

• Let the iron come back up to temperature.

• Then reheat the joint and try again.

And if precision soldering is not your major problem, take a look at the next issue.

2. Burned and Overheated Components

Once I heard that a customer of our competitor ranted about the burned components that he kept receiving on his PCB, got frustrated and decided to try us out for a change of supplier, and that is totally uncool. Well, their demise is our gain.

The issue happens most commonly due to unchecked or ignoring the reflow requirements details in the data sheet, causing mistakes soldering that can lead to short circuits.

3. Poorly Manufactured Components

There is always a possibility of acquiring a poorly manufactured PCB. Some signs and symptoms include loose components, connection issues, even a bad solder or left over flux. One example of a bad solder job is a cold solder. This symptom occurs when the soldering technician fails to properly heat the solder at a through hole or surface mount connection joint. This causes a bad connection and has the potential to lead to burnt components and power issues. Leftover flux, a substance used to aid in the soldering process, can also do harm to your component as it can cause corrosion on a PCB. And I cannot forget to mention components installed incorrectly or wrongly placed, too.

4. Issues with Quality of the Silkscreen

Silkscreen is normally used on the component side to identify components, test points, PCB and PCBA part numbers, warning symbols, company logos and manufacturer marks. But occasionally we'll see some low-quality issues involving the silkscreen on the circuit board such as unclear edges, blur and ink smearing. This is because that the method used by the factory to process the silkscreen is done by hand. For goodness sake, we're not living in the dinosaur age anymore! And I don't get why many companies are still buying this.

The picture above shows that both the same Gerber files containing the logo and text sent to 2 different factories. The PCB on the left clearly displaying a better quality of silkscreen compared to the one on the right.

5. Plating Voids

Plated thru-holes are copper-coated holes in a printed circuit board. These holes allow electricity to be carried from one side of the circuit board to the other. To create these holes, the PCB fabricator drills holes through the circuit board, puncturing the material all the way through. A layer of copper is then added to the surface of the material and along the walls of these holes through an electroplating process. This process deposits a thin layer of electroless copper onto the circuit board in a process called deposition. After this step, extra layers of copper are added and etched to create the circuit image.

While effective, the deposition process is not perfect, and under certain circumstances can result in voids in the plating. Plating voids are effectively gaps or holes in the plating of the circuit board, and are usually the result of problems during the deposition process. These plating voids are particularly problematic because imperfections in the plating of a thru-hole prevent an electrical current from passing through the hole, resulting in a defective product.

These plating voids happen because, for one reason or another, the material does not coat evenly during the deposition process. The reasons for this include contamination of the material, air bubbles caught in the material, insufficient cleaning of the holes, insufficient catalyzation of the copper in the deposition process or rough hole drilling. Any of these problems can result in plating voids along the walls of the circuit holes.

Defects as a result of contamination, air bubbles or insufficient cleaning can be avoided by cleaning the material properly after drilling. Additionally, defects from faulty drilling can be avoided by closely following the manufacturer’s directions during use, such as recommended number of drill hits, drill in-feeds and drill speeds. Both problems can be avoided by hiring a well-qualified and experienced PCB manufacturing company.

6. PCBs Sourced from Exceptionally Cheap Markets

Wonder why issue No.1 – 5 happens? This could be the reason why. You may want to find the most bargainable PCBs manufacturer available in the market to maximize your budget. Don't get me wrong, I'm not saying cheap equals to low quality. Even firms like us want to give you the best price we can offer; however, so often the cheapest that they offered does not necessarily guarantee or do justice in terms of the quality.

Some of the companies also notoriously offer their products at very low prices in online quotes, but so often customers check out only to realize that the price has been summed up. Below are some of the reviews taken from the so called “cheap PCB” sites.

7. Unattended Quality Check

Let's be honest, the quality checking step is perhaps the most important part in the whole PCB manufacturing process. Sadly, many companies will often overlook this, and often failures of PCB can be avoided by having a professional QC. Quality checking includes but is not limited to:

• Checking silkscreen of components

• Inspect the board by using the Oscilloscope device to check the signal

• Orientation and polarity checking

• IC pins shorted checking

• Components malfunction and missing pieces check

• Short circuit test

• Power-on test

• Functional checking

At Smart Prototyping, we strive to be one of the best PCB/PCBA manufacturers in the market. With our humble team of experienced PCB enthusiasts, we can take a look at your PCB files and run a complete and thorough quality check to ensure you the best quality of PCBs in the market at an ever affordable price. Get in touch with us today and turn your project into an awesome masterpiece!